The present invention relates to a blank for use in forming a sealing cap for a bottle, and the invention also relates to a cap when formed from such a blank.
It has also been proposed to provide a flat blank for forming into a sealing cap for a bottle, the blank comprising an inner circular upper cap part, and an annular peripheral side part surrounding the upper cap part, and an element intended to provide a tear-off means which extends radially outwardly from the side part of the cap, there being a pair of score lines formed in the material of the blank which extend from the vicinity of the tear-off means to positions on the opposite side of a central point of the blank.
One blank of this type is described in Swedish Pat. No. 216,716. In this known cap blank the annular peripheral side part of the cap is provided at the sides of the tear-off means, which are in the form of a tear-flap, with a pair of softly rounded recesses. The score lines, which are arcuate, extend symmetrically in the direction of the axis of the tear-flap from the vicinity of the tear-flap to points on the opposite side of the central region of the blank. The score lines start just inside but slightly away from the said recesses. Initially the score lines converge but the convergence decreases towards the central region of the blank and subsequently the score lines diverge. It is to be appreciated that the central region of the blank is a common central region for the inner circular upper cap part and the surrounding annular peripheral side part of the cap.
The flat cap blank described in Swedish Pat. No. 216,716 may be converted into a cap for a bottle by means of a deep drawing operation. The flat peripheral region of the cap is then reshaped to form a cylindrical side or skirt of the finished cap. During the deep drawing operation the material at the periphery of the flat blank cap will be displaced inwards to the smaller diameter of the cylindrical region of the finished cap. Thus, if the score lines did run parallel in this side region of the cap they would be subjected to deforming lateral forces during the deep drawing operation which would cause wear, uncontrolled alteration of shape, and even rupture of the score lines, and thus the cap would be difficult to remove from the mouth of the bottle or other container. This problem has been appreciated, but no final solution to the problem has yet been proposed.
When a cap manufactured from a blank as described above is mounted on a bottle the cap firmly engages the peripheral rib provided at the mouth of the neck of the bottle. When the bottle is to be opened the tear-flap is pulled, and two symmetrical side segments are formed which tend to maintain what might be termed as "claw-grip" upon the neck of the bottle. In order to remove the cap the tear-flap must be pulled so hard during the opening process that the peripheral rib provided at the mouth of the bottle deforms the two segments of the cap sufficiently to enable them to release their claw-grip around that rib. It has been found that the present caps, when used on beer bottles and the like, may be difficult to remove, especially when dried beer etc. forms between the glass and the cap and acts as an adhesive. The above described design of score lines causes an inwardly directed lateral force to be generated during the tearing process, thus tending to increase the claw-grip of the cap on the bottle.